tracing: add support for userspace stacktraces in tracing/iter_ctrl

Impact: add new (default-off) tracing visualization feature

Usage example:

 mount -t debugfs nodev /sys/kernel/debug
 cd /sys/kernel/debug/tracing
 echo userstacktrace >iter_ctrl
 echo sched_switch >current_tracer
 echo 1 >tracing_enabled
 .... run application ...
 echo 0 >tracing_enabled

Then read one of 'trace','latency_trace','trace_pipe'.

To get the best output you can compile your userspace programs with
frame pointers (at least glibc + the app you are tracing).

Signed-off-by: Török Edwin <edwintorok@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/stacktrace.h b/include/linux/stacktrace.h
index b106fd8e0d5c..68de51468f5d 100644
--- a/include/linux/stacktrace.h
+++ b/include/linux/stacktrace.h
@@ -15,9 +15,17 @@ extern void save_stack_trace_tsk(struct task_struct *tsk,
                                 struct stack_trace *trace);
 
 extern void print_stack_trace(struct stack_trace *trace, int spaces);
+
+#ifdef CONFIG_X86
+extern void save_stack_trace_user(struct stack_trace *trace);
+#else
+# define save_stack_trace_user(trace)              do { } while (0)
+#endif
+
 #else
 # define save_stack_trace(trace)                        do { } while (0)
 # define save_stack_trace_tsk(tsk, trace)               do { } while (0)
+# define save_stack_trace_user(trace)              do { } while (0)
 # define print_stack_trace(trace, spaces)               do { } while (0)
 #endif